A glutamic acid

Figure 1.9 Examples of functionally important intrinsic metal atoms in proteins, (a) The di-iron center of the enzyme ribonucleotide reductase. Two iron atoms form a redox center that produces a free radical in a nearby tyrosine side chain. The iron atoms are bridged by a glutamic acid residue and a negatively charged oxygen atom called a p-oxo bridge. The coordination of the iron atoms is completed by histidine, aspartic acid, and glutamic acid side chains as well as water molecules, (b) The catalytically active zinc atom in the enzyme alcohol dehydrogenase. The zinc atom is coordinated to the protein by one histidine and two cysteine side chains. During catalysis zinc binds an alcohol molecule in a suitable position for hydride transfer to the coenzyme moiety, a nicotinamide, [(a) Adapted from P. Nordlund et al., Nature 345 593-598, 1990.)...

This reaction requires the formation of an hydroxide ion, as in the enzyme reaction. A proper reference reaction for the first step in the enzyme would then be simply the proton transfer from a water molecule to a glutamic acid in solution ... 

The digestion of the protein, after heme removal, using Glu-C endoproteinase was also carried out. This enzyme cleaves the polypeptide backbone on the carboxyl terminus of a glutamic acid residue and in this case yielded twelve chromatographic responses. Despite two of these arising from unresolved components, molecular weight information was obtained from 15 polypeptides, one of which was the intact protein, covering the complete sequence, as shown in Table 5.10. 

Nguyen, K.T., Kau, D., Gu, J.Q. et al. (2006) A glutamic acid 3-methyltransferase encoded by an accessory gene locus important for daptomycin biosynthesis in Streptomyces roseosporus. Molecular Microbiology, 61 (5), 1294-1307. 

The main lines of this approach were later embodied in an enantioselective synthesis of (—)-a-allokainic acid (Scheme 34) (179). The sole stereo center of die ene reaction starting material was derived from a glutamic acid derivative (132) to avoid loss of optical activity via double bond migration (see Scheme 33), the a acid function of kainic acid had to be reduced before the pyrolysis step... 

All the evidence presented in this section concerns aspartic acid residues, and one may wonder whether glutamic acid residues display similar reactivity. The answer is clearly that they do not, in particular for entropy reasons. In fact, replacement of a reactive aspartic acid residue by a glutamic acid residue can greatly increase the chemical stability of a peptide. This is exemplified by human epidermal growth factor (hEGF), an important promoter of... 

In 2-OG dependent enzymes ferrous iron is bound in the active site by the 2-His-l-carboxyIate facial triad. The carboxylate is either an aspartic acid or a glutamic acid. In the beginning the slightly distorted... 

The active site of the enzyme contains two distinct regions an anionic region that contains a glutamic acid residue, and a region in which a histidine imidazole ring and a serine hydroxyl group are particularly important. 

The active site of the enzyme contains a glutamic acid residue that is ionized at pH 7 and supplies the base. A histidine residue, partially protonated at pH 7, in turn supplies the proton necessary to form the common enol (Figure 13.6). 

Sickle cell anemia is caused by synthesis of a mutant form of hemoglobin, hemoglobin 5 or HbS), in which a glutamic acid at position 6 of the hemoglobin (3 subunit is replaced by valine. 

Finally, when oxazolones 269 bearing a carboxyalkyl chain at C-4 were used, the separation was effected on the mixture of diastereomeric succinimides 270 and 271. In this case, the resolved amino acid contains both an aspartic acid and a glutamic acid side chain (Scheme 7.87). Selected examples of amino acids that illustrate the general applicability of Obrecht s methodology are shown in Table 7.22 (Fig. 7.24). 

The glycosidases act by two different mechanisms which is revealed by the stereochemistry at the anomeiic centre of the product (McCarter and Withers, 1994). In one type of glycosidases the anomeiic centre is directly attacked by a hydroxide to give a product with inverted stereochemistry at the anomeiic centre. In the other mechanism, the anomeric centre is attacked by the carboxylate group of a glutamic acid residue to form an intermediate in which the carbohydrate moiety is covalently bound to the enzyme similar to in epoxide hydrolases (Figure 2.16) and serine hydrolases. Attack on this intermediate by a nucleophile leads to the net result which is retention of the stereochemistry at the anomeric centre. 

Title Process for the Preparation of Poly-a-Glutamic Acid and Derivatives Thereof... 

Observations Poly-a-glutamic acid containing amine and carboxylic acid end groups... 

Brignon et al. (1969) demonstrated that the maximum acid-binding capacity of /3-lactoglobulin D is the same as that of the other variants. The curves are identical at pH 4.0. At pH 6.5, one less proton is dissociated in the titration of the D variant than with the B variant, as would be predicted from the substitution of a glutamine residue for a glutamic acid residue in B. The anomalous carboxyl group observed in the other variants is also detected in the D variant. 

Another common crosslink is an amide formed between the y-carboxyl group of a glutamic acid side chain and an amino group from a lysine residue.307 This isopeptide linkage is formed from a residue of gluta-mine through the action of the enzyme transglutaminase (Eq. 2-23). Isopeptide crosslinks are found in hair, skin, connective tissue, and blood clots. 

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